Transmissions or gear-boxes are used in a variety of applications to change the speed and torque provided by a prime mover such as an automotive engine, wind power system, or wind turbine. Two or more gears are used in transmission of rotational motion, torque and power from on rotating shaft to another.
A familiar use of gears is in power transmission of an automobile. The engine, rotation at high speed, delivers power to the transmission, which gears reduce the speed at which the power is transmitted to the drive shaft. Thus the wheels rotate at a speed much lower than that at which the engine turns.
One type of arrangement of gears in many types of transmissions and gearboxes are planetary gear sets. Planetary gear sets are compact and optimized combination of gears to transfer torque from one rotating shaft to another.
A prior art planetary gear set has four parts which are the sun gear, the ring gear, and planet gears and the planet carrier. In one configuration, the sun gear rotates, causing the planet gears to rotate about the sun gear. The planet gears are inside of the ring gear, which rotates at a reduced speed.
Conventional planetary gear sets are limited in speed ratios to no more than 9:1. Higher speed ratios require a stack of planetary gear sets, also known as multiple stage gear sets. The use of a stack reduces the compactness of the gear set and increases the complexity of the device as well as decreases efficiency.
It is desirable to have planetary gear set with high speed ratios for a variety of applications.